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Sunday, July 10, 2005

A German light cruiser design study, circa 1914

I am unsure of the exact year that this was intended to be laid down, but I have estimated that it was for 1914. I had originally hoped that it would be only 4,240 tons displacement. At this point, I am unsure if that was Standard or normal. The speed was set at 32 knots, maximum. To achieve adequate strength, the machinery had to be light and the normal displacement had to be greater. In this case, it was 4,950 tons with a draft of 18ft instead of 16ft. The armament was 4-6in QF guns with 8-21in TT in twin mountings. The armor basis was 2in. This is the Springsharp report:
Ger/CL/1914, Enter country Enter ship type laid down 1914 (Engine 1921)

Displacement:
 4,574 t light; 4,716 t standard; 4,950 t normal; 5,137 t full load

Dimensions: Length overall / water x beam x draught
 450.87 ft / 450.00 ft x 41.00 ft x 18.00 ft (normal load)
 137.43 m / 137.16 m x 12.50 m  x 5.49 m

Armament:
      4 - 6.00" / 152 mm guns in single mounts, 108.00lbs / 48.99kg shells, 1914 Model
   Breech loading guns in deck mounts with hoists
   on centreline, evenly spread
   Aft Main mounts separated by engine room
 Weight of broadside 432 lbs / 196 kg
 Shells per gun, main battery: 180
 8 - 21.0" / 533.4 mm above water torpedoes

Armour:
   - Belts:  Width (max) Length (avg)  Height (avg)
 Main: 2.00" / 51 mm 360.00 ft / 109.73 m 8.00 ft / 2.44 m
 Ends: Unarmoured
 Upper: 2.00" / 51 mm 250.00 ft / 76.20 m 8.00 ft / 2.44 m
   Main Belt covers 123 % of normal length
   Main belt does not fully cover magazines and engineering spaces

   - Armour deck: 1.00" / 25 mm

Machinery:
 Oil fired boilers, steam turbines, 
 Geared drive, 2 shafts, 61,617 shp / 45,967 Kw = 32.00 kts
 Range 3,900nm at 12.00 kts
 Bunker at max displacement = 422 tons

Complement:
 294 - 383

Cost:
 £0.639 million / $2.557 million

Distribution of weights at normal displacement:
 Armament: 54 tons, 1.1 %
 Armour: 632 tons, 12.8 %
    - Belts: 400 tons, 8.1 %
    - Torpedo bulkhead: 0 tons, 0.0 %
    - Armament: 0 tons, 0.0 %
    - Armour Deck: 232 tons, 4.7 %
    - Conning Tower: 0 tons, 0.0 %
 Machinery: 2,120 tons, 42.8 %
 Hull, fittings & equipment: 1,767 tons, 35.7 %
 Fuel, ammunition & stores: 376 tons, 7.6 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   2,805 lbs / 1,272 Kg = 26.0 x 6.0 " / 152 mm shells or 0.6 torpedoes
 Stability (Unstable if below 1.00): 1.24
 Metacentric height 2.0 ft / 0.6 m
 Roll period: 12.3 seconds
 Steadiness - As gun platform (Average = 50 %): 60 %
   - Recoil effect (Restricted arc if above 1.00): 0.33
 Seaboat quality  (Average = 1.00): 1.19

Hull form characteristics:
 Hull has rise forward of midbreak
 Block coefficient: 0.522
 Length to Beam Ratio: 10.98 : 1
 'Natural speed' for length: 21.21 kts
 Power going to wave formation at top speed: 63 %
 Trim (Max stability = 0, Max steadiness = 100): 50
 Bow angle (Positive = bow angles forward): 2.00 degrees
 Stern overhang: -1.00 ft / -0.30 m
 Freeboard (% = measuring location as a percentage of overall length):
    - Stem:  25.00 ft / 7.62 m
    - Forecastle (20 %): 23.00 ft / 7.01 m
    - Mid (33 %):  23.00 ft / 7.01 m (15.00 ft / 4.57 m aft of break)
    - Quarterdeck (15 %): 15.00 ft / 4.57 m
    - Stern:  15.00 ft / 4.57 m
    - Average freeboard: 17.80 ft / 5.43 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 147.2 %
  - Above water (accommodation/working, high = better): 94.6 %
 Waterplane Area: 12,540 Square feet or 1,165 Square metres
 Displacement factor (Displacement / loading): 93 %
 Structure weight / hull surface area: 70 lbs/sq ft or 340 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.91
  - Longitudinal: 2.46
  - Overall: 1.00
 Hull space for machinery, storage, compartmentation is cramped
 Room for accommodation and workspaces is adequate

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